Conversion of hydrocarbons



Feb. 22, 1944.

K. D. UITT! CONVERSION OF HYDROCARBONS Filed Sept. 9, 1940 lll/TAKES 0 BUTAAfEspPkop/yvz' POLYMER/Z/IBLE 0L EFINS Patented Feb. 22, 1944 2,342,383

UNITED STATES PATENT oFFicE (YIONVEESIONZIzIsYsDROCBBONS l l l Kenneth D.l Ulttl, Chicago, lll., assignor to 'Universal Oil Products Company, Chicago, lll., a corporation of Delaware Application september s, 1940, semina. 355.957

This is a continuation-impart of my co-pending application Serial No. 297,392, illed September The invention is directed to an improved meth-v od of producing liquid fractions of highantiknock value boiling within the range of gasoline from normally gaseous hydrocarbons,v such as butanes the several conversion steps into selected fractions, the process involves a dehydrogenating system wherein butanes or butanes and propane are converted into substantial yields of corresponding olens, followed by separate catalytic polymerization oi' the butylenes and propylene thus produced to convert the same into high yields of liquid polymers boiling within the range of gasoline and of good antiknock value. The butylene polymerizing step being followed -by catalytic hydrogenation of the polymer gasoline produced therein to form a hydrogenated polymer product of improved antiknock value. Residual butanes which remain unconverted after subjecting the butane-buty1ene fractions from the dehydrogenating operation to catalytic polymerization treatment are returned to the dehydrogenating operation for further conversion into readily polymerizable oleflns. Residual propane, which remains unconverted after subjecting the propanepropylene fraction from the dehydrogenating'operation to catalytic polymerization, may also beV returned to the dehydrogenating operation to convert substantial quantities thereof into propylene.

The dehydrogenating operation may be either catalytic or thermal and when both propane and butanes are to be dehydrogenated, they may be subjected to dehydrogenation in commingled state or separately. The preferred method of operation, when separate hydrogenatlng steps are employed, is to separate the materials to be dehydrogenated into a fraction consisting predominantly of normal butanes and a fraction consisting prewhich will give good yields of iso-butylene and 2 Claims. (Cl. 26o-683.1)

propylene, whereas such thermal treatmentof the normal butanes would result in the excessive production of light gases and only minor yields of butylenes. Separate catalytic dehydrogenation of the normal butanes, on the other hand, may be controlled to give good yields of butylenes.

The polymerizing operation, towhlch butanes and butylenes recovered from the products of the dehydrogenating operation are supplied, is conducted in the presence of a polymerizing catalyst under conditions regulated t convert substantially all of both 'the iso and normal butylenes into high yields of liquid polymers boiling within the range of gasoline, leaving' butanes as the essential components ofI the normally gaseous fractions in the resulting products andk thereby serving as a means of isolating substantially pure `butanes for further dehydrogenating treatment in addition to its function knock polymer gasoline.

The polymer gasoline producedin the butylene polymerizing operation will contain substantial quantities of iso-octenes formed by polymerization of the iso-butylenes and may advantageously be hydrogenated to'i'orm-a saturated polymer of producing good anti- 'gasolineL of improved antiknock value and low bromine f number or acid heat test, suitable for aviation l gasoline. This product contains substantial quantities of iso-octanes formed by hydrogenation of the iso-octenes. The hydrogenat- A ing operation is catalytically conducted and preferably employs light hydrogen-containing gases formed in the dehydrogenating operation as a i source of hydrogen.

'I'he polymerizing operation, to which propane and propylene separately recovered from the l products of the dehydrogenating operation are supplied,- also employs a polymerizing catalyst K and is operated to convert substantially all of the propylene into high yields of liquid polymers boiling within the range of gasoline and of good dominantly of isobutane and propane, catalytiy antiknock value. Hydrogenation o! this product is not contemplated since such treatment will not improve its antiknock value. Due to its olenic nature, it does not meet the acid-heat test requirements for aviation gasoline, but is highly desirable for blending with straight-run or cracked gasoline of inferior antiknock value to form a good antiknock motor pylene polymerizing step. in addition to its function of producing good antiknock polymer gasoline, serves to isolate substantially ypure propane from propylene, since the propane remains substantially unconverted while the propylene is polymerized. The propane thus obtained may,

gasoline. The prowhen desired, be recycled to the dehydrogenating operation for the production therefrom of addi- Y tional quantities of propylene.

will be found advantageous and are believed to involve paten'table novelty. Each of the in-v dividual steps of the .process and 'the coopera-` tive combination thereof, which constitutes the integrated process disclosed, will be discussed in greater detail in conjunction with the description oi the accompanying drawing.

Figure 1 of the drawing is essentially a flow diagram illustrating'the cooperative relationship between the various major steps of the process andv Figure 2 is aA diagrammatic illustration'oi the dehydrogenating operation as employed for thermally dehydrogenating a mixture o! isobutane and propane with separate catalytic dehydrogenation of normal butanes.

Referring now to Figure l of the drawing, the

normally gaseous hydrocarbons tc be dehydrogenated. which'may consist predominantlyr oi" butanes or may comprise both butanes and propane, are supplied from any desired source through line i to the dehydrogenating system 2 wherein they are subjected to either catalytic or thermal dehydrogenation treatment under con-n ditions regulated to produce therefrom suhsi'arlV tial yields of readily polymerizable olens, such as butylenes or butylenes and propylene.

The products oi the dehydrogenating opera`= tion are directed from the dehydrogenating sys tem 2 through line 3 to` separation into the desired selected fractions in zone e* which comprises fractionating, condensing and collec equipment of anysuitable well hnown rorrn.

When the dehydrogenating operation involves the thermal conversion of either butanes or propane or a mixture thereof, side reactions, such as cracking andpolymerisation, which ac-v company the thermal dehydrogenation treatment will result in the production of some nor--A mally' liquid fractions -tvhich are removed' from separating zone 4 through-line to storage or elsewhere, as desired. A normally gaseous trac tion, consisting predominantly o butanes and butylenes, is separately recovered from the products of the dehydroeenating operation and directed from zone d through line d to the .butylene poiyinerizing sys' l, which `will he later described. Another normally gous ilrac`= tion, consistingv essentially of pro :fr t and propylene, is separately recovered from the prod ucts of 4the dehydrogenating operation and directed from zone vd through line d to the propylene polymerizing system e, which will be later described. A fraction consisting essentially of gases having 2 and less carhon atoms in the molecule and containing hydrogen gas formed in the dehydrogenating operation are separately removed from zone v4 through line iii and may be removed, all or in part, fr the system through line Il' .to storage or elsewhere. as desired, or preferably, regulated quantitiesoi the hydrogen-containing ygases are utilised :as a source of hydrogen in the catalytic hydrogenatdeleterious ing operation succeeding the butylene' polymerizing step. When so utilized. hydrogen-contain# ing gases are directed from line i0 through line l2 to the catalytic hydrogenating system I9, which will be later described.

'Ihe dehydrogenation of paraiilnc hydrocarbon gases having 3 and 4-carbon atoms in the molecule is only one methodof producing butylenes and propylene for polymerization. Hydrocarbon oil cracking operations, either thermal or catalytic, comprise another well known source vof such materials and the invention speciilcally contemplates the polymerization of propylene and/or butylenes from any external source, together with the corresponding olefins formed in the dehydrogenating operation. This may be accomplished, for example, by supplying a mixture of normally gaseous fractions containing substantial quantities of the desired olens, such as, for example, olefin-containing gases produced in the cracking of hydrocarbon oils, to the same separating system whereto the products of the dehydrogenating operation are supplied. In the case here illustrated, such extraneous gases may .be introduced into the system by supplying the same through line i3 to separating zone 4 or extraneous normally gaseous fractions, consisting predominantly of butanes'and butylenes, may be supplied to the butylene polymerizing system through line it and, when desired, extraneous noally gaseous fractions, consisting predoantly of propane and propylene, may be supplied to the propyiene polymerizing system through line' i5.

The butylene polymerizing system l is operated to convert substantially all of the butylene components of the fi-carbon atom gases supplied thereto and such polymerization is accomplished in the presence or a catalyst capable of promoting this reaction. The catalyst which l preferahly employ is the well known solid phosphoric acid catalyst which consists essentially of granules or preformed pellets or a relatively inert porous carrier, such as diatomaceous earth or kies r impregnated `with a mixture of ortho and pyro phosphoric acids and calcined prior to their use. catalysts of this ltype are preferably employed inthe forni ci one or a plurality of stationary heds through which the reactants are passed after being heated to the temperature required for conducting the reaction. Since the poiyroerizing reaction is strongly excthermic,

,provision is preferably made for preventing an excessive temperature rise in the catalyst hed heat exchanger type and circulating a cooling Ruedi therethrough in indirect heat exchange relation with the catalyst and the reactants and conversion products. Provision may also be made; sehen desired, for periodically reactivating the catalyst in situ by burning therefrom heavy conversion products deposited thereon dtrrtf' the conversion reaction in a stream or dingen-containing gases'. It is also portant to obtain an optimum degree or hyeration or the catalyst during processing and particularly 1 g reactivation. ese features are all taught in the prior art and illustration or the various means whereby they may he accomped is, therefore, unnecessary in the present instance.

lt is' also possible to ist substantially oplet@ conversion of the huwlenes inI the hutylene polymerizins step with other well known uns.; catalysts, such as.' for example, sulc acid either in` liquid state orA on a relatively as fol...

2,342,383 A i j I `and wherein the hydrogenated polymer product phosphoric acid may also be employed-as may aluminum chloride, preferably in conjunction with hydrogen chloride, and boron iluoride, preferably in conjunction with hydrogen. Any of these or other known polymerizing catalysts capable of accomplishing the desired results may be employed within the scope of the invention.

l Operating conditions under which substantially complete polymerization of the butylenes may be accomplished are also familiar to those skilled in the art. They will varyconsiderably depending upon the catalyst employed and the ratio of isobutylene to `normal butylenes in the charge. When employing solid phosphoric acid catalyst at temperatures of from about 300 to about 550 F. will be found suitable, preferably with a superatmospheric pressure which may range from 200 to 1500 pounds, or thereabouts, per square inch'.

In general, more severe conditions should be'employed with increased ratios of'normal to isobutylene and/or with decreased contact time inv normally liquid products formed inthe polymerizing operation are directed from zone Il through line 29 to storage or elsewhere, as desired.v 'I'he residual normally gaseous products of the poly-v merizing operation, which will consist predominantly of butanes, are separately removed fromzone il and recycled throughline 2| to the dehydrogenating operation for further conversion therein to produce additional yields of readily polymerizable olens.

Hydrogenation of the polymer gasoline produced in the butylene polymerizing step is accomplished in hydrogenating system I9 in the presence of a catalyst which promotes the hydrogenating reaction. One of the catalysts which has been found most suitable for this purpose consists essentially of nickel on porous particles of a relatively inert siliceous carrier, such as diatomaceous earth or kieselguhr. This catalyst may be produced, for example, by precipitating nickel carbonate on the carrier, pressing or extrudlng the mixture into pills or pellets which are dried and reduced in an atmospheric ofyhydrogen at a temperature of the order of 750 F. However, the specific nature of the hydrogenating catalyst and the method of its manufacture are not a novel part of the present invention and any other well known hydrogenating catalyst may be employed within its scope. Some of the other materials which are suitable comprise, for example, oxides of chromium, molybdenum andl tungsten either alone or in combination and with a nickel catalyst of the nature above mentioned. The desired hydrogenating reaction may be' accomplished at a tem- 1 perature of from 250 to 450 F. or thereabouts, and at a superatmospherlcv pressure of from to250 pounds or more persquare inch.

The products of thehydrogenating operation are supplied from zone I9 through line 22 to separating zone 23 which may comprise suitable fractionating equipment of auywell known form lpropylene Dolymerizing system may be of is separated from the unused hydrogen or hydrogen-containing gases. I'he hydrogenated Polymer gasoline, which will include substantial quantities of iso-octanes and is a'substantially saturated' product of low bromine number and of materially improvedv antiknock value, as compared with the polymer gasoline from which it is formed, is withdrawn from zone 29 through line 24 to storage or elsewhere, as desired. Hydrogen or hydrogen-containing gases are removed from zone 23 through line 25 and may be discharged,

all or in part, from the system. Preferably, however, since a quantity of hydrogen considerably in excess of that theoretically required to accomplish substantially complete hydrogenation of the unsaturated polymer gasoline is required for best results, hydrogen or hydrogen-containing gases from zone' 23 are preferably recycled to the hydrogenating zone through lines 2B and l2 in quantities regulated to maintainthe desired excess of hydrogen from this zone. When hydrogen or hydrogen-containing gases formed in the de-` hydrogenating operation are-not employed as the solesource of hydrogen in zone i9, hydrogen or gases rich in hydrogen may be supplied to zone` I9 from an external source through line 21.

The propylene polymerizing operation is conducted in zone 9 in the presence of a polymeriz- 'ing catalyst under conditions regulated to convert all or substantial quantitiesl of the propylene into high yields of liquid polymers, a large portion of which boil within the vrange of gasoline and are of high antiknock value. Solid phosphoric acid catalyst. of the natureabove mentioned is preferably employed in thisl step, al i though any other well known polymerizing. catalystl capable of accomplishing the desired results may be employed within the scope of the invention. With the solid phosphoric `acid catalyst, the the same general type referred to in conjunction with the preceding description of the butylene polymerizing system. Temperatures of the order of 350 to 550- F., or thereabouts, and a superatmospheric pressure within the approximate range of 200 to 1500 pounds per square inch may be employed in the propylene polymerizing system when the solid phosphoric `acid catalyst is utilized.

The products resulting from the propylene poly'- merizing operation are directed from zone l through line 29 to the succeeding separating system 29 which will ordinarily comprise a plurality of fractionating steps of any suitable well known form. Polymer gasoline of the desired end-boiling point is removed from zone l29 through line III to storage or elsewhere. as desired. H eavier liquid products formed in the polymerizing operation are separately removed from zone 29 through line Il to vstorage or elsewhere, as desired. The residual normally gaseous products of the propylene polymerizing step, which will consist pre- 4dominantly'oi propane. are separately withdrawn from zone 29 through line I2 and may be removed from the system or, when desired. may be re= cycled, all or in part. "through line 32 to the de# hydrogenatng system for further conversion therein to produce additional yields of prowlene.

Referring now to Figure 2, whiclnae previously mentioned, diagrammatically illustrates *a more specific embodiment of the dehydrogenatins stage of the system illustrated in Figure l. a separating zone 34 is provided preceding the dehydrogenating zone, to which separating zone theresidual butanes (both iso and normal) inem4 separating zone I1 of Figure 1 are supplied through line 2 l The charging stock, which may be butanes or a mixture of butanes and propane is also supplied to separating zone 34 through line I.

Separating zone may comprise any suitable well known form of fractionating equipment and its function is tov separate from the normally gaseous materials supplied thereto, a fraction consisting predominantly of normal butanes and a fraction consisting predominantly of iso-lontanevof the dehydrogenatingsystem and the iso-butane or mixture of iso-butane and propane is directed from zone 34 through line 30 to the thermal dehydrogenating zone 2B of the dehydrogenating system together with propane, from the propylene polymerizing step. of Fig. l., supplied through line 33. Products resulting from the catalytic dehydrogenation treatment of the normal butanes are removed Yilrom zone 2A through line 3A, while the products resulting from the thermal dehydrogenation treatment of the so-butane and propane are removed trom zone 2B through line 3B and. in the case here illustrated, both streams of products are directed through line 3 to theseparating system 4 of Figure 1.

The operating conditions required for dehydrogenating various parailinic hydrocarbons are now well known to those skilled in the art. Pressures and temperatures, and particularly the latter may v w be varied considerably with different contact times and somewhat different conditions are optlmum with different catalysts, which latter are now well known. It is therefore considered unnecessary to discuss in detail all of the many possible variations and the following will serve to illustrate suitable conditions under which the preferredembodiment of the process provided by the invention may be conducted using a catalyst for dehydrogenating the normal butanes which consists essentially of preformed relatively porous pellets or granules of alumina or other refractory material and one or more of the oxides of chromium, molybdenum, vanadium and cerium, and employing thermal dehydrogenating conditions for the mixture of iso-butane and propane.

- The catalytic dehydrogenation operation may employ a temperature of from 1000 to 1200 F.,.or thereabouts, with `a-pressure-whlch does not exceed 100 pounds per square inch, or thereabouts, lower pressures down to substantially atmospheric being preferred. f The space velocity, expressed as cubic feet or reactants subjected to treatment per hour, per cubic feet 4of ,space occupied bythe catalystbed is preferably within the range of 1000 to 2000 for converting normal butanes and 500 to 1500 for converting a mixture of butanes and propane. f 4

The thermal dehydrogenating operation is also preferably conducted at substantially atmospheric or relatively low superatmospheric pressure although higher pressures 'up to '150 pounds or more per square inch may be employed when desired. The temperature employed. may range from 1050 to 1200 F., or thereabouts and the conversion time is preferably within the range of 50 to 150 seconds for mixtures of iso-butane and propane. A shorter time factor which may range.

5 for example, from 20v to 60 seconds is preferred when substantial quantitiesof normal butanes are present.

Either thermal. or catalytic dehydrogenation of a mixture of iso and normal butanes, alone or l@ with'propane, may be accomplished within the vrange of conditions above given, but thermal treatment of theY normal butanes, either alone yor in adxnixture, underfthese conditions will result in extensive cracking thereof with consequent low` yields of butylenes and high yields of lighter gases. Thermal treatmenty is of course, less expensive andl may be employed for converting the iso-butane and propane with less cra/cking than in the case of normal butanes. Low pressure operation is preferred in any ease to high pressure and is essential in catalytic dehydrogenation. High pressure operation is less expensive in thermal dehydrogenation but favors cracking and therefore isV preferredv only when high yields of butylenes, which will polymerize to a higher octane number product as compared with that resulting from the polymerization of propylene, are not essential, i. e. when the process f is operated for the production? ofhigh yieldsof motor gasoline rather than high yields of aviation gasoline.

Y As an example of one specific operation of the process, which is not to be construed as a limitation; the charging stock supplied to the dehydrogenating system is a mixture of iso and normal butane from an external source, to which residual butanes from the butylene polymerizing step andvresidual propane from the propylene polymerizing step are addedf The `butanes are separated by fractionation into two components one of which consists predominantly of iso-butane Y and the other consisting predominantly of normal-butane. The iso-butane is commingled with a fractionv consisting predominantly of propane from the propylene polymerizing step and the mixture `is subjected to thermal dehydrogenation -at a temperature of approximately 1070 F. and

at substantially atmospheric pressure, the time during which it is exposed` to these conditions being about 100 seconds. The normal Vbutane fraction is subjected to catalytic dehydrogenation, in thepresence of a catalyst of the preferred type above mentioned, at a temperature of approxi- The butane-butylene fraction from the dehydrogenating. system is subjected to catalytic polymerization in the presence of solid phosphoric acid catalyst at a temperature of approximately 'I0 375 F. and at a superatmospheric pressure ofl about 1000 pounds per square inch, with a space velocity of approximately 20 gallons of reactants per hour, per cubic feet of space occupied by the catalyst bed. l 7l Normally gaseous fractions of the Yproducts re.

mately 1100 F., and at substantially atmospheric pressure, with a space velocity of about 1500 cubic` .feet per hour, per cubicf feet of space occupied by hydrogen in the light gas stream from the dehydrogenating system. The hydrogenating zone is operated at a temperature of approximately 350 F. and at a superatrnospheric pressure of about 200 pounds per square inch. Unused hydrogen is recycled and the hydrogenated polymer gasoline is recovered. This product amounts to approximately 23 gallons per thousand cubic feetof butanes charged to the system. It has an octane number of approximately 90 as determined by the motor method and, being substantially saturated, is well withinthe acid heat test requirements for aviation gasoline.

The propane-propylene fraction derived from the dehydrogenating system is subjected to separate catalytic polymerization, using solid phosphoric acid as the polymerizing catalyst, at a temperature of approximately 425 F., and a superatmospheric pressure of about 1200 pounds per square inch, the space velocity being ap.-

' proximately 18 gallons per hour per cubic feet of space occupied by the catalyst bed;

s Normally gaseous fractions of the ,products from the propylene polymerizing step, which consist predominantly of propane, are recycled to the thermal .dehydrogenating step. The polymer gasoline produced in the propylene polymerizing operation is recovered and amounts to approximately 2 gallons per thousand cubic feet oi' bu- 45 tane charging stock supplied to the system. It has an.. octane number of approximately 83, as

determined by the motor method and is suitable for blending with gasoline' of interior antiknock value to improve the octane rating o! the latter.

I claim as my invention: v

1. A process for producing more valuable products from a hydrocarbon mixture` containing butanes and propane which comprises separating from said mixture a fraction consisting predominantly of normal butanes and a fraction' consisting predominantly o1' isobutane and propane,

catalytically dehydrogenating the rst-named fraction and thermally dehydrogenating the second-mentioned fraction, commingling and seite arating fromthe resultant products a butanei butene fraction and' a propane-propene fraction,

subjecting the butane-butene fractionto Polymerization, subjecting the propane-propene fraction to polymerization under independentlyI con trolled conditions, returning residual normal butane from the mst-mentioned polymerizing step to the catalytic dehydrogenating step, and returning residual propane from the second-mentioned polymerizing step to the thermal dehydrogenating step.

2. The process as dened in claim 1 further characterized in that the residualbutane is returned'to the catalytic dehydrogenating step by being supplied tothe mst-mentioned separating step for treatment therein together with. said hydrocarbon mixture while theI residual propane is returned to the thermal dehydrogenating step `by being commingled with said isobutane and'` propane from the first-mentioned step.

mum n. 

